High frequency apparatus



p 11, 1956 c. o. LUND 2,762,950

HIGH FREQUENCY APPARATUS Filed A ril 16, 1951 1 11 I F9 .l

SUPPZY 17 INVENTOR ATTORNEY United States Patent HIGH FREQUENCY APPARATUS Christian 0. Land, Copenhagen, Denmark, assignor to Radio Corporation of America, a corporation of Delaware Application April 16, 1951, Serial No. 221,291 6 Claims. (Cl. 315-39) magnetic fields.

Some high-frequency and microwave apparatus may necessitate the use of current and/or voltage carrying circuitry disposed within a cavity resonator or a waveguide. It' conventional conducting means are employed in high-frequency apparatus, such as waveguides or cavity resonators, the high-frequency fields may be distorted and/ or undesirable reflections or energy losses may occur.

The apparatus of this invention permits one to conduct a current or voltage through a hollow, radio-frequency wave transmission means such as a Waveguide, coaxial line, or the like, without substantial interaction with the field of the waves transmitted through the transmission means. The apparatus comprises an unshielded, conductive helix which extends into the wave transmission means, and is oriented with its longitudinal axis parallel to the electric line of force of the radio-frequency field and normal to the magnetic lines of force of this radio-frequency field. The helix, so oriented, acts as a high impedance to the radio-frequency energy within the wave transmission means and substantially no radio-frequency current is induced in the helix.

In a specific form of the invention, the wave transmission means comprises a length of rectangular waveguide dimensioned to support the propagation of radiofrequency waves in the TEM mode. Within the waveguide is a heater filament. The filament leads comprise helically wound conductors which extend into the waveguide normal to the broad walls thereof and parallel to the narrow walls thereof.

The invention, and embodiments thereof, will be described in greater detail with reference to the accompanying drawings in which Figure 1 is a perspective view of a typical embodiment wherein a pair of helices disposed within a rectangular hollow pipe waveguide, according to the invention, for supplying filament current to a noise diode; Figures 2 and 3 are front and side views, respectively, of electric and magnetic field configurations excited in the waveguide of Figure 1 when a TEo,1 Wave is being propagated within the waveguide, Figures 4 and 5 are front and side views, respectively, of a cavity resonator of circular section in which a helix is disposed, according to the invention, the helix axis coinciding with the axis of the resonator and within which resonator a TE1,1,1 wave configuration is excited; and Figures 6 and 7 illustrate electromagnetic configurations in the cavity resonator of Figure 4 when a TMO,1,1 Wave is excited therein.

Like reference characters are applied to like elements throughout the drawing.

Referring to Figure 1 of the drawing, the current carrying conductors for a filament electrode 5 comprise a pair of helices 1, 3 all disposed in the evacuated space between a pair of energy permeable mica windows 6, 7

enclosing a section of rectangular hollowpipe waveguide 8. The filament 5 comprises the cathode electrode of a noise diode and is spaced approximately ten millimeters from one broad wall 9 of the waveguide 8, that wall functioning as the anode of the diode. The space enclosed by the mica windows 6, '7 comprises the diode envelope.

Although it is possible to insert straight conductors through the narrow walls 20 of the waveguide 8 for supplying filament current to the diode, the close proximity of the filament 5 to the anode electrode 9 makes difiicult the problem of physically supporting these straight conductors and the filament 5. This problem is especially important since the electrode spacing is generally of a critical nature. Straight conductors inserted into the guide through the broad walls 9, 11 of the waveguide 8 are usually unsatisfactory for most energy propagation modes because of resulting wave reflections and because the conductors absorb energy from or distort the highfrequency fields.

These difiiculties are obviated for the rectangular waveguide 8, according to the invention, by orienting the helices 1, 3 such that their respective longitudinal axes are normal to the waveguides broad walls 9, 11, and parallel to the waveguide electric axis. The helix 1 connected to one end of the filament 5 is returned to a filament supply 13 through an aperture insulator 15 located in the broad wall 11 opposite the diode anode 9. The remaining helix 3, connected to the other end of the filament 5,

is returned to the supply 13 by a relatively short straight conductor 17, normal to the axis of the helix 3, passing through an aperture insulator 19 in a narrow Wall 20 of the waveguide 8. It may 'be desirable, for manufacture or design purposes, to return the helices 1, 3 to the supply 13 through both narrow or both broad walls. The arrangement herein shown indicates that either may be done.

Assuming that TEo,1 wave energy is coupled to and propagated within the waveguide 8 of Figure 1, electric and magnetic field configurations set up therein are illustrated in Figures 2 and 3. By comparing Figures 1, 2, and 3 it is evident that the electric lines of force, for the TEo,1 mode, are normal to the helices 1, 3. The magnetic lines of force, extending in the direction of energy propagation in the waveguide 8, are in space quadrature with the electric force lines and do not substantially link any turns of the helices 1, 3.

While the foregoing embodiment, according to the invention, describes the advantages of helices for conducting means for the rectangular waveguide 8, there is other apparatus with which the helices, disposed according to the invention, may be used. For example, a single helix may be inserted through an aperture in the outer condoctor of a coaxial transmission line and connected to the inner conductor such that the longitudinal axis of the helix is normal to the inner and outer conductors. In this way the helix may serve to apply a desired potential to the inner conductor, without reaction upon the field between the conductors.

Referring to Figures 4 and 5, electromagnetic field configurations are illustrated for a TE1,1,1 wave excited within a cavity resonator 21 of circular section. A helix 1, disposed as illustrated with its longitudinal axis coincident with the axis of the circulator resonator 21, conducts current through the high-frequency fields existing therein without the helix 1 substantially coupling to these fields. The electric force lines are substantially normal to the helix 1 and the magnetic lines of flux eifectively do not link the helical turns. Similarly, referring to Figures 6 and 7, a helix 1 maybe disposed in the resonator 21 wherein a TMo,1,1 configuration is excited. It again may be seen that the helix 1 in the circular cavity resonator 21 is not substantially affected by the high-frequency fields existing therein.

While electric and magnetic field configurations are shown for several modes in which energy may be propagated or excited, there are many other suitable modes which may be coupled to and excited in hollow pipe waveguides, coaxial transmission lines, and cavity resonators. The main criterion for satisfactory operation is that there be substantially no coupling between the helix 1 and high frequency fields propagated within the waveguide. Then there are no currents induced in the helix and the fields associated with the high-frequencies in the waveguides or cavity resonators are generally undisturbed.

What is claimed is:

1. In a radio frequency circuit of the type including a length of rectangular Waveguide having broad and narrow walls and dimensioned to support the propagation of radio frequency wave energy in the TE01 mode, and an element in said waveguide it is desired to supply with current, means for conducting current to said element without substantial interaction with the radio frequency field of said waveguide comprising, at least one unshielded, conductive helix conductively connected at one end portion to said element and insulated from said waveguide, said helix extending normal to the broad walls of said waveguide and parallel to the narrow walls of said waveguide, whereby the axis of said helix is parallel to the electric lines of force of said radio frequency field.

2. An electron discharge device comprising, in combination, a length of rectangular waveguide having broad and narrow walls and dimensioned to support the propagation of radio frequency wave energy in the TEOI mode; a filament comprising a length of wire located in said waveguide adjacent and parallel to one of the broad walls of said waveguide and normal to the waveguide axis, said one broad wall serving as the anode of said discharge device; and means for conducting energizing current to said filament without substantial interaction with the radio frequency field of said waveguide comprising, a pair of unshielded conductive helices one connected at one end portion to one end portion of said filament and the other connected at one end portion to the other end portion of said filament, said helices being insulated from said Waveguide walls, and each helix extending normal to 4 the broad walls of said waveguide and parallel to the narrow walls of said waveguide, whereby the axes of said helices are parallel to the electric lines of force of said radio frequency field.

3. In combination, a hollow wave transmission means dimensioned to support the propagation of radio frequency energy, and means for introducing a potential into said wave transmission means without substantial interaction with said radio frequency energy comprising an unshielded helix of wire extending into said wave transmission means, said helix of wire being disposed in said Wave transmission means with its longitudinal axis parallel to the electric lines of force of the field of said radio frequency energy and normal to the magnetic lines of force of the field of said radio frequency energy.

4. In the combination as set forthin claim 3, said hollow wave transmission means comprising a hollow-pipe waveguide.

5. In the combination as set forth in claim 3, said hollow wave transmission means comprising a cavity resonator.

6. In combination, a hollow wave transmission means dimensioned to support the propagation of radio-frequency energy, and a conductor arranged in said wave transmission means to avoid substantial interaction with said radio-frequency energy comprising an unshielded helix of wire disposed in said wave transmission means with its longitudinal axis parallel the electric lines of force of the field of said radio-frequency energy and normal to the magnetic lines of force of the field of said radio-frequency energy.

References Cited in the file of this patent UNITED STATES PATENTS 2,106,770 Southworth et al. Feb. 1, 1938 2,122,538 Potter July 5, 1938 2,153,728 Southworth Apr. 11, 1939 2,241,976 Blewett et al May 13, 1941 2,423,327 Lafferty July 1, 1947 2,452,317 Ner-gaard Oct. 26, 1948 2,463,368 Finke Mar. 1, 1949 2,506,644 Johnson May 9, 1950 2,559,581 Bailey July 10, 1951 

